Facsimile telegraph scanning mechanism



June 17, 1958 J. v. FOLL ETAL FACSIMILE TELEGRAPH SCANNING MECHANISMOriginal Filed July 11, 1955 @ZKFO LL United States atent Ofilice2,839,603 Patented June 17, 1 958 FACSIMILE TELEGRAPH SCANNING MECHANISMJohn Victor Foll, Peter William Sieber, and Alan Arthur Kirchel,Beckenham, England, assignors to Muirhead & Co. Limited, Beckenham,England Original application July 11, 1955, Serial No. 521,151. Dividedand this application November 13, 1956, Serial No. 621,745

3 Claims. (Cl. 178-71) This application is a division of our co-pendingapplication Serial No. 521,151.

The invention relates to facsimile mechanisms such as are employed infacsimile transmitters or receivers, wherein the sheet containing thematter to be transmitted, or the sheet upon which the reproduction is tobe made, is mounted upon a drum for the purpose of being scanned, thedrum being driven rotationally and arranged for relative axial movementwith respect to an optical system. The sheet is usually attached to thedrum either by longitudinal clips which engage the two ends of the sheetor by means of a transparent spring-tensioned wrapper. In either case itis desirable that the drum be held in a particular rotational positionduring the unloading and loading operations in order that the clips mayreadily be placed in position or, in the case of a transparent wrapper,that the free end of the wrapper is presented in a convenient positionfor manipulation and loading.

It is essential that the scanning drums in the transmitter and receiverrespectively should rotate in correct angular relationship with respectto each other and in exact synchronism. Consequently the drums and therelated mechanism must be manufactured to a high degree of precision.Each drum with its arrangement for holding the sheet is of substantialweight and it is desirable that means be provided to ensure that thespeed of the drum has been reduced to a low level before it is stoppedautomatically in the desired position for loading and unloading.

In certain applications of facsimile telegraph machines it is desirablethat the driving motors of the transmitter and receiver should runcontinuallyin synchronism and that either drum may be stopped,re-started and synchronized with the other by automatic means. Theacceleration and synchronization of the drum which is being restartedmust be carried out without imposing such a load on its driving motor aswill pull it out of synchronism.

The invention consists of a facsimile scanning mechanism having meansfor stopping the drum is a desired position, so arranged that they areprevented from engaging until the speed of the drum has been reduced toa low level, and means operative upon disengaging the stopping means toaccelerate the drum to a speed slightly above its normal speed until itis in correct angular relationship with the remote scanning drum.

The invention will be further described in conjunction with theaccompanying drawings in which:

Figure 1 shows an embodiment of the invention.

Figure 2 is an enlarged view of a detail of the embodiment of Figure 1.

Figure 3 shows a modification of the invention.

Figure 1 shows an elementary scanning mechanism in which a rotatablemessage drum 35 is slideably mounted on a hollow shaft 36 and is movedaxially by part nut 37 pivotally mounted in one end of the drum engagingthe lead screw 34 extending within the hollow shaft, through a slot 38in the hollow shaft, the lead-screw being driven by gear wheels 58, 59,60 and 61, at a speed different from that of the drum to effect anendwise movement of the drum. The part nut 37 may act as a key to causethe drum to rotate at the speed of the hollow shaft or alternativelyother axially-slideable keying means may be provided.

Attached to the hollow shaft is gear wheel 39 driven by gear wheel 40which in turn is driven frictionally by clutch plates 41 keyed to shaft42. Shaft 42 is driven by a gear wheel 43 mounted thereon. Gear wheel 43is one of a train of gear wheels 43, 44, 45 and 46 driven by thesynchronous motor 47. When the motor is running synchronously gear wheel46 is driven at the designed operating speed of the drum, while gearwheel 39 fixed to the hollow shaft is driven in the same direction at aslightly greater speed (since it is slightly smaller than gear wheel46). Gear wheel 39 has fixed to it a lug 48 which operates inconjunction with permissive latch 49 mounted on gear Wheel 46 so thatwhereas gear wheel 46 can rotate when gear wheel 39 is stationary, gearwheel 39 when it rotates cannot overtake gear wheel 46 beyond the pointwhen lug 48 has caught up the latch 49. In this condition gear wheel 40will slip between the friction plates 41.

The thrust of the friction plates 41 is applied by spring 50 the forceof which can be removed by operation of the start-stop lever 51leftwardly in which case there is no drive to gear wheel 39 and the drum35 will stop. Associated with the lever 51 is an arresting lever 52which, when the lever 51 is moved to the stop position, is free toengage with a rectangular hole 53 in the gear wheel 39 under theinfluence of a spring 54.

In the rest position of the drum, gear wheel 39 is held by the arrestinglever 52 so that drum 36 is in the convenient position for fixing themessage clips or operating the wrapper. In this position the drum can bemoved endways to the start-traverse position, the release of the nut 37being effected by pressing tail 55 against spring action towards thestop 56 mounted on the end of the drum. Motor 47 will uninterruptedly bedriving gear 46 at the synchronous speed and in the correct phasecorresponding to the associated remote telegraphic machine.

To commence scanning, the lever 51 will be moved to the start positionallowing spring 50 to exert its thrust on friction plates 41 to drivegear wheels 40 and 39. At the same time the arresting lever 52 will bedisengaged from the gear wheel 39. Hence the drum 35 will accelerate androtate at a slightly faster speed than the gear wheel 46 until the lug48 abuts against the latch 49 after which time the drum will revolve atthe speed of gear wheel 46 and in correct phase and synchronism with thedrum of the remote telegraphic machine. Lead screw 34 associated withpart nut 37 will traverse the drum past the lens system 57. Whenscanning is complete and it is required to stop the drum for reloadingand resetting, movement of the lever 51 to the stop position willrelease the driving clutch plates 41 and move the arresting lever 52towards the gear wheel 39 to engage with hole 53 to stop the drum as itcomes around by its own momentum to the required position.

In order that the impact of stopping the drum 35 is reduced to anacceptable amount, provision is made so that the speed of the drum willhave reduced considerably before the arresting lever 52 engages with theslot 53 to stop the drum suddenly and hold it in its rest position (seeFigure 2).

The arresting lever 52 is chamfered as shown at 62, and clearance 64 isprovided between the length of slot 53 and the length of the projectinglug of lever 52, so that when the arresting lever 52 approaches gearwheel 39 rotating at its working speed, the arresting lever will fallpartially into the slot 53 and the edge 63 will engage tent that thearresting lever falls into the slot sufficiently for-leading edge 65 toengage slot end 63.

In these circumstances the shock will be small enough so asto not damagethe arresting lever projection as it enters the slot and holds the drumin the desired rest position.

In alternative arrangements the friction clutch may be replaced by othertypes of clutch capable of slip, e. g., employing a viscous liquid, aneddy current, or a magnetic or hysteresis torque.

Figure 3 shows a modification of the invention. The scanning mechanismis covered by a lid 66 which may be swung about two pivots .67 .(one ofwhich is shown). When the 'lid is open start-stop lever 51 is in thestop position in which clutch 41 is disengaged and lever 52 is engagedwith gear 39 to hold drum 35. When lid 66 is closed an extension .68engages start-stop lever 51, which is moved to the right, thuswithdrawing arresting lever 52 'from engagement with gear 39 andallowing clutch 4.1 to engage. The drum then commences to revolve and isaccelerated up to a speed slightly higher than scanning speed, aspreviously described, vuntil latch 48 engages stop 49, when the speed ofdrum 35 is reduced to that required for scanning.

What we claim is:

l. Facsimile scanning mechanism comprising a message drum, a synchronousmotor, gearing to transmit the drive from said motor to said drum, anoptical systems, a lead-screw to produce relative axial movement betweensaid drum and said optical system, a clutch interposed in said gearing,said gearing including agear having a slot in its face and coupled tosaid drum, an arresting lever having a lug adapted to engage said slotin said gear to stop said drum, a spring urging said arresting leverinto said slot, a control lever arranged to disengage said clutch andthen to allow said arresting lever to enter said slot when moved to thestop position, said arresting lever lug being so chamfered and of such alength in relation to the slot, that it can only fully enter said slotto stop said drum when the speed of said drum has fallen below apredetermined level.

2. Facsimile scanning mechanism, as claimed in claim 1, comprising asecond gear mounted co-axially with the drum and continuously driven bythe motor at the desired scanning speed, a stop mounted on said secondgear, a permissive latch coupled to the gear, said gear being driven ata speed higher that the desired scanning speed, said latch and said stopbeing arranged so that said second gear may rotate whilst said gear isstationary but said gear can only overtake said second gear until saidlatch engages said stop after which the clutch slips.

3. Facsimile scanning mechanism, as claimed in claim 2, comprising a lidto cover said mechanism, said lid having an extension which engages thecontrol lever, arranged so that opening said lid allows said controllever to move to the position in which the arresting lever is engagedwith the gear and closing said lid moves said control lever to theposition in which said arresting lever is disengaged from the gear.

References Cited in the file of this patent UNITED STATES PATENTS2,288,135 Hoza June 30, 1942 2,630,495 Wise Mar. 3, 1953 2,652,448 HuntSept. 15, 1953

